JPH09105412A - Magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid bringing a protection bearing into a state to make contact with a rotary shaft during the rise of rotation of the rotary shaft, to prevent the occurrence of co-rotation, and to normally increase the number of revolutions up to the ordinary number of revolutions. SOLUTION: A conical trapezoidal part 24 having a taper surface (even a contact surface having a curvature mey be employed) axially linearly changed is formed between the large part 21 and the middle part 22 of a rotary shaft 2. The taper surface of the conical trapezoidal part 24 is formed in such a manner to make contact with the edge on the inner surface side of the inner ring 17 of a protection bearing 7. This constitution brings the taper surface of the conical trapezoidal part 24 of the rotary shaft 2 into contact with the edge on the inner surface side of the protection bearing 7. Thus, since, during the rise of rotation of the rotary shaft 2, whirling of the rotary shaft 2 is supported by a protection bearing 7 through the taper surface of the trapezoidal conical part 24, swirling of the rotary shaft 2 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device applied to a turbo molecular pump or a main shaft of a machine tool.

[0002]

2. Description of the Related Art Conventionally, as a magnetic bearing device incorporated in a turbo molecular pump and used, for example, a triaxial control type as shown in FIG. 8 is known. This magnetic bearing device has a cylindrical mounting frame 1 whose both ends are open, and a high frequency motor 3 for driving a rotating shaft 2 is arranged in the center of the mounting frame 1. The rotary shaft 2 is configured to be magnetically supported in the radial direction by a radial bearing 4 and magnetically supported in the axial direction by a thrust bearing 5.

The radial bearing 4 includes a radial electromagnet 41 mounted on the inner peripheral surface of the mounting frame 1 and a radial electromagnet 4.
Rotor core 42 attached to rotary shaft 2 corresponding to 1
And formed from The thrust bearing 5 includes an axial electromagnet 51 attached to the inner peripheral surface of the mounting frame 1, an armature disc 52 and a permanent magnet 53 integrally attached to the lower end of the rotary shaft 2, and a permanent magnet facing the permanent magnet 53. 54
And formed from In order to protect the radial bearing 4 or the thrust bearing 5 from the abnormal rotation of the rotary shaft 2 and the like on the inner peripheral surface on the upper side of the mounting frame 1 and the inner peripheral surface of the axial electromagnet 51,
Protective bearings 6, 7 such as rolling bearings are provided.

The rotating shaft 2 comprises a large diameter portion 21, a medium diameter portion 22 inserted into the protective bearing 7, and a small diameter portion 23 to which an armature disc 53 and the like are attached.
1, the medium diameter portion 22 and the small diameter portion 23 are formed so that the diameter thereof becomes smaller in this order. After inserting the spacer 8, the armature disk 52, and the permanent magnet 53 into the small-diameter portion 23 of the rotating shaft 2, the nut 9 is screwed to the tip of the small-diameter portion 23, whereby the armature disk 52 and the permanent magnet 53 are joined together. The armature disc 52 is fixed to a predetermined position of 23 and the axial electromagnet 51 is opposed to the armature disc 52.

A radial sensor 10 for detecting the radial displacement of the rotary shaft 2 is mounted on the inner peripheral surface of the mounting frame 1. Further, an axial direction sensor 11 for detecting the axial displacement of the rotary shaft 2 is arranged in a fixed state at a predetermined position below the rotary shaft 2 in the axial direction. Next, the operation of the magnetic bearing device shown in FIG. 8 will be described. The rotating shaft 2 is magnetically levitated by the radial electromagnet 41 and the axial electromagnet 51.
The radial sensor 10 detects the radial displacement of the rotary shaft 2, the axial sensor 11 detects the axial displacement of the rotary shaft 2, and both detected displacements are input to a control circuit (not shown). . The control circuit obtains the radial position and the axial position of the rotary shaft 2 based on the detected displacement, and compares the obtained position with the target position of the rotary shaft 2,
The radial electromagnet 41 is set so that the rotary shaft 2 is at the target position.
And each exciting current of the axial electromagnet 51 is controlled.

When the high frequency motor 3 is energized, the rotating shaft 2 magnetically levitated at the target position in this way is gradually accelerated from the stationary state to the rated speed.

[0007]

However, when the rotation of the rotary shaft 2 is started up, when the rotational speed of the rotary shaft 2 reaches the vicinity of the primary resonance point (resonance point of the rigid mode), the rotary shaft 2 is rotated. 2 swings around greatly. However, in the conventional three-axis control type magnetic bearing device used for the turbo molecular pump, no means for controlling or preventing whirling of the rotary shaft 2 at the time of starting the rotary shaft 2 is particularly provided. .

For this reason, the rotating shaft 2 randomly collides with the protective bearing 7 or comes into contact with the protective bearing 7 after the collision, and the protective bearing 7 rotates together with the rotating shaft 2 so that the rotating speed does not increase and the rated rotating speed is reached. It had the drawback of not reaching. Therefore, it is an object of the present invention to prevent the protective bearing and the rotating shaft from coming into contact with each other at the start of rotation of the rotating shaft, and thereby to rotate the rotating shaft normally to reach a steady rotating speed.

[0009]

According to a first aspect of the present invention, there is provided a rotary shaft, a radial bearing for magnetically supporting the radial direction of the rotary shaft, and a thrust for magnetically supporting the axial direction of the rotary shaft. The rotary shaft and the protective bearing are formed so as to be freely contactable with each other in a three-axis control type magnetic bearing device including a bearing and a protective bearing that protects the radial bearing and the thrust bearing. The object is achieved by providing control means for controlling the rotating shaft and the protective bearing so as to temporarily contact each other at the time of rising.

According to a second aspect of the present invention, in the magnetic bearing device according to the first aspect, an inclined surface is formed on at least one of the rotary shaft and the protective bearing at a contact portion between the rotary shaft and the protective bearing. The rotating shaft and the protective bearing are brought into contact with each other to achieve the above object.

According to a third aspect of the present invention, a rotary shaft and a radial bearing that magnetically supports the rotary shaft in the radial direction,
A three-axis control type magnetic bearing device including a thrust bearing that magnetically supports the rotating shaft in the axial direction and a protective bearing that protects the radial bearing and the thrust bearing, and suppresses whirling of the rotating shaft. By providing a rotating shaft whirling suppressing bearing, when the rotation of the rotating shaft rises, the rotating shaft whirling suppressing bearing is provided with control means for controlling the bearing to temporarily support the rotating shaft. Achieve the purpose.

[0012]

According to the present invention, the control means controls the rotary shaft so that the rotary shaft and the protective bearing temporarily contact each other when the rotation of the rotary shaft rises. By being received, whirling of the rotating shaft is suppressed.

According to the second aspect of the invention, when the rotation of the rotary shaft rises, the rotary shaft and the protective bearing are temporarily contacted,
Since the whirling of the rotating shaft is received by the protective bearing, the whirling of the rotating shaft is suppressed. In the invention according to claim 3, since the control means controls the rotation shaft whirling suppression bearing so as to temporarily support the rotation shaft when the rotation of the rotation shaft rises. It is received by the whirling suppression bearing, and whirling of the rotating shaft is suppressed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows the configuration of the thrust bearing 5 and the protective bearing 7, which are the main parts, in the magnetic bearing device of the first embodiment of the present invention. In addition,
The magnetic bearing device according to the first embodiment has substantially the same configuration as the magnetic bearing device described in FIG. 8 except for the thrust bearing 5 and the protective bearing 7, and therefore, the same parts are designated by the same reference numerals. Are omitted as appropriate.

In this magnetic bearing device, as shown in FIG. 1, a frustoconical portion 24 having a tapered surface linearly changing in the axial direction is provided between the large diameter portion 21 and the medium diameter portion 22 of the rotary shaft 2.
The tapered surface of the truncated cone 24 is formed so as to be in contact with the inner surface side edge of the inner ring 71 of the protective bearing 7. The contact surface (tapered surface) of the truncated cone 24 is shown in FIG.
A contact surface having a curvature, that is, a contact surface that changes in a curved line in the axial direction may be used, such as the truncated cone portion 24A shown in FIG. 4A or the truncated cone portion 24B shown in FIG. Further, the frustoconical portion 24 and the inner ring 71 of the protective bearing 7 may come into contact with each other at three or more points.

FIG. 2 shows the configuration of the control system of the magnetic bearing device of FIG. The control system of this magnetic bearing device is
In order to control the magnetic levitation position of the rotary shaft 2 to the target positions of the radial bearing 4 and the thrust bearing 5, and to suppress whirling of the rotary shaft 2 when the rotation of the rotary shaft 2 rises,
A control circuit 12 for controlling the axial position of the rotary shaft 2 is provided.

That is, the radial direction sensor 10, the axial direction sensor 11, and the rotation speed sensor 16 for detecting the rotation speed of the rotary shaft 2 are connected to the input side of the control circuit 12, and the radial electromagnet is connected to the output side of the control circuit 12. 41 and the axial electromagnet 51 are connected. Then, the control circuit 12 obtains the position of the rotating shaft 2 based on the detected displacements of both the radial sensor 10 and the axial sensor 11, compares the obtained position of the rotating shaft 2 with the target position, and Each exciting current of the radial electromagnet 41 and the axial electromagnet 51 is controlled so as to reach the target position. Further control circuit 1
In addition to the control described above, the reference numeral 2 designates a protective bearing for the tapered surface of the truncated cone 24 of the rotary shaft 2 when the rotation of the rotary shaft 2 rises.
Of the rotary shaft 2 by temporarily contacting the inner surface side edge of the inner ring 71 of
The control is performed to suppress the whirling.

Next, the operation of the first embodiment configured as described above will be described. Now, when the power is turned on, the rotary shaft 2 of the magnetic bearing device is magnetically levitated by the radial electromagnet 41 and the axial electromagnet 51. The radial displacement of the rotary shaft 2 detected by the radial sensor 10 and the axial displacement of the rotary shaft 2 detected by the axial sensor 11 are input to the control circuit 12. The control circuit 12 calculates the radial and axial positions of the rotary shaft 2 based on the detected displacement, compares the calculated position of the rotary shaft 2 with the target position, and sets the radial electromagnet so that the target position is reached. Each exciting current of 41 and the axial electromagnet 51 is controlled.

When the rotation of the rotary shaft 2 rises (starts), the radial target position of the rotary shaft 2 is the center position of the radial bearing 4. As shown in FIG. 3 (A), the axial target position of the rotary shaft 2 is a position where the tapered surface of the truncated cone portion 24 comes into contact with the inner surface side edge of the inner ring 71 of the protective bearing 7, and It is assumed that the own weight of No. 2 is not applied to the inner surface side edge of the inner ring 71. Therefore, the control circuit 1
2 is a radial electromagnet so that the determined radial and axial positions of the rotary shaft 2 are the target positions thereof, and that the weight of the rotary shaft 2 is not applied to the inner surface side edge of the inner ring 71. Each exciting current of 41 and the axial electromagnet 51 is controlled.

When the high-frequency motor 3 is energized, the rotating shaft 2 magnetically levitated at the predetermined position in this way is gradually accelerated from the stationary state to the rated speed.
However, when the rotation of the rotary shaft 2 is started up, the tapered surface of the truncated cone 24 of the rotary shaft 2 is in contact with the inner surface side edge of the inner ring 71 of the protective bearing 7 in the axial direction of the rotary shaft 2 as described above. Controlled by. Therefore, even when the number of rotations of the rotary shaft 2 reaches the vicinity of the primary resonance point (resonance point of the rigid mode) at the rising of the rotation of the rotary shaft 2, the whirling of the rotary shaft 2 is reduced by the tapered surface of the truncated cone 24. Is received by the protective bearing 7, the rotary shaft 2 does not swing around greatly.

After that, when the rotation speed of the rotation shaft 2 detected by the rotation speed sensor 16 passes the primary resonance point, the axial target position of the rotation shaft 2 is changed to the steady rotation position. 3 rises from the state of FIG. 3 (A) to be in a non-contact state with the protective bearing 7 as shown in FIG. 3 (B). When the rotating shaft 2 rises, the truncated cone portion 24 has a tapered surface,
The rise is quick and smooth. After that, the rotating shaft 2
So that its axial position is the position of steady rotation,
It is controlled by the control circuit 12.

According to the first embodiment described above, the rotary shaft 2
The tapered surface of the truncated cone portion 24 of the rotary shaft 2 is brought into contact with the inner surface side edge of the protective bearing 7 when the rotation of the rotary shaft rises. Therefore, when the rotation of the rotary shaft 2 rises, it is possible to avoid the protective bearing 7 and the rotary shaft 2 from entraining each other even after passing the resonance point, so that the steady rotation speed can be reached.

In the first embodiment described above, the conical trapezoidal portion 24 is provided on the rotary shaft 2, and the tapered surface of the conical trapezoidal portion 24 is allowed to come into contact with the inner surface side edge of the inner ring 71 of the protective bearing 7. However, the present invention may have any form as long as the rotary shaft 2 and the protective bearing 7 can contact each other. For example, the rotary shaft 2 has the same structure as that shown in FIG. 21
The inner surface side of the inner ring 71 may be formed in a funnel shape so that the lower end edge of the inner ring 71 can freely contact the inner ring 71 of the protective bearing 7. In addition, the rotary shaft 2 and the protective bearing 7 are
The surface contact may be made at the start of the rotation.
In this case, the inner surface side of the inner ring 71 of the protective bearing 7 is formed in a funnel shape so that the frustoconical portion 24 of the rotary shaft 2 comes into surface contact.

Next, a magnetic bearing device according to a second embodiment of the present invention will be described. The magnetic bearing device of the second embodiment has substantially the same configuration as the magnetic bearing device described in FIG. 1 except for the thrust bearing 5 and the protective bearing 7, and therefore the same parts are designated by the same reference numerals. The description thereof will be omitted as appropriate.

FIG. 5 shows the structure of the thrust bearing 5 and the protective bearing 7 in the magnetic bearing device of the second embodiment. In this magnetic bearing device, as shown in FIG. 5, the permanent magnet 53 attached to the lower end of the rotary shaft 2 has a truncated cone portion 5 having a tapered surface that linearly changes in the axial direction.
31 is provided so as to project downward, and the frustoconical portion 531 is configured to be borne by the rotary shaft whirling motion suppression bearing 13 that suppresses whirling of the rotary shaft 2 when the rotation of the rotary shaft 2 rises. To be done. The contact surface (tapered surface) of the truncated cone portion 531 may not only linearly change in the axial direction but also curved in the axial direction, that is, a contact surface having a curvature.

The rotary shaft whirling suppression bearing 13 is formed of a rolling bearing or the like, and the inner surface side of the inner ring 131 thereof is formed in a funnel shape so that the truncated cone-shaped portion 531 of the permanent magnet 53 can be inserted therethrough for bearing. Further, the rotation shaft whirling suppression bearing 13 is configured to be able to reciprocate between the position shown in FIG. 5 and a predetermined position below the position by using a solenoid (not shown) or the like.

As described above, the conical trapezoidal portion 531 is formed on the permanent magnet 53 side, and the rotary shaft whirling suppression bearing 13 is correspondingly formed into a funnel shape, as will be described later. When the whirling suppression bearing 13 moves up and down,
This is so that the operation can be performed smoothly.

FIG. 6 shows the configuration of the control system of the magnetic bearing device of FIG. In the control system of this magnetic bearing device, the magnetic levitation position of the rotary shaft 2 is controlled to the target positions of the radial bearing 4 and the thrust bearing 5, and the rotary shaft 2 is controlled.
In order to suppress whirling of the rotating shaft 2 when the rotation of the rotating shaft rises, a control circuit 14 that controls the axial position of the rotating shaft whirling suppressing bearing 13 is provided.

That is, the radial direction sensor 10, the axial direction sensor 11, and the rotation speed sensor 16 for detecting the rotation speed of the rotary shaft 2 are connected to the input side of the control circuit 14, and the radial electromagnet 41 and the shaft are connected to the output side thereof. The directional electromagnet 51 and the solenoid 15 for reciprocating the rotating shaft whirling suppression bearing 13 as described above are connected. Then, the control circuit 14 includes the radial sensor 10 and the axial sensor 11
The position of the rotary shaft 2 is calculated based on both detected displacements of the two, and the calculated position of the rotary shaft 2 is compared with the target position. Each exciting current is controlled.
In addition to the above control, the control circuit 14 further controls the rotary shaft 2
The position of the rotating shaft whirling motion suppressing bearing 13 is controlled so that the rotating shaft 2 is temporarily supported by the rotating shaft whirling motion suppressing bearing 13 at the start of rotation.

Next, the operation of the second embodiment thus constructed will be described. Now, when the power is turned on, the rotary shaft 2 of the magnetic bearing device is magnetically levitated by the radial electromagnet 41 and the axial electromagnet 51. The radial displacement of the rotary shaft 2 detected by the radial sensor 10 and the axial displacement of the rotary shaft 2 detected by the axial sensor 11 are input to the control circuit 14. The control circuit 14 obtains the radial and axial positions of the rotary shaft 2 based on the detected displacement, compares the obtained position of the rotary shaft 2 with the target position, and sets the radial electromagnet so that the target position is reached. Each exciting current of 41 and the axial electromagnet 51 is controlled. Since the control circuit 14 excites the solenoid 15 prior to the start of the rotation of the rotary shaft 2, the rotary shaft whirling suppression bearing 13 is arranged in the direction shown in FIG.
It is in the position shown in FIG.

When the high frequency motor 3 is energized, the rotary shaft 2 magnetically levitated at the target position in this way is gradually accelerated from the stationary state to the rated speed.
However, when the rotation of the rotary shaft 2 is started up, as described above, the truncated cone portion 53 of the permanent magnet 53 integrated with the rotary shaft 2 is formed.
1 is temporarily inserted into the bearing 13 for suppressing whirling of the rotating shaft to be received. Therefore, even when the rotation speed of the rotating shaft 2 reaches the vicinity of the primary resonance point (resonance point of the rigid mode) at the start of rotation of the rotating shaft 2, the whirling motion of the rotating shaft 2 is caused by the magnet 5.
Since the tapered surface of the truncated cone-shaped portion 531 of No. 3 is received by the rotating shaft whirling suppression bearing 13, a large whirling of the rotating shaft 2 is suppressed.

After that, when the rotation speed of the rotation shaft 2 detected by the rotation speed sensor 16 passes through the primary resonance point, the control circuit 14 deenergizes the solenoid 15, so that the rotation shaft whirling suppression bearing 13 is From the position shown in FIG.
As shown in (B), the permanent magnet 53 is lowered to a predetermined position.
It is in a non-contact state with the truncated cone-shaped portion 531 and maintains that state. After that, so that the rotary shaft 2 reaches the target position,
It is controlled by the control circuit 14.

According to the second embodiment described above, the rotary shaft 2
At the start of the rotation of, the truncated cone-shaped portion 531 of the permanent magnet 53 integrated with the rotating shaft 2 is temporarily supported by the rotating shaft whirling suppression bearing 13. Therefore, when the rotation of the rotary shaft 2 rises, it is possible to avoid the protective bearing 7 and the rotary shaft 2 from entraining each other even after passing the resonance point, so that the steady rotation speed can be reached.

[0034]

As described above, according to the magnetic bearing device of the present invention, whirling of the rotary shaft is suppressed when the rotation of the rotary shaft rises, so that the protective bearing and the rotary shaft have resonance points. Even if it passes, it is possible to avoid entrainment and to reach a steady rotation speed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magnetic bearing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a control system of the magnetic bearing device.

FIG. 3 is a diagram illustrating an operation of the magnetic bearing device.

FIG. 4 is a view showing another example of the truncated cone portion of the magnetic bearing device.

FIG. 5 is a sectional view of a magnetic bearing device according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a control system of the magnetic bearing device.

FIG. 7 is a diagram illustrating an operation of the magnetic bearing device.

FIG. 8 is a schematic cross-sectional view showing a configuration of a conventional magnetic bearing device, and hatching is appropriately omitted as necessary to make the drawing easy to see.

[Explanation of symbols]

 1 Mounting Frame 2 Rotating Shaft 3 High Frequency Motor 4 Radial Bearing 5 Thrust Bearing 6 Protective Bearing 7 Protective Bearing 8 Spacer 9 Nut 10 Radial Sensor 11 Axial Sensor 12 Control Circuit 13 Rotating Shaft Whirl Suppression Bearing 14 Control Circuit 15 Solenoid 16 Rotation speed sensor 21 Large diameter part 22 Medium diameter part 23 Small diameter part 24, 24A, 24B Cone trapezoidal part 41 Radial electromagnet 42 Rotor core 51 Axial electromagnet 52 Armature disk 53, 54 Permanent magnet 71 Inner ring 131 Inner ring 531 Cone trapezoidal part

Claims (3)

[Claims] 1. A rotary shaft, a radial bearing that magnetically supports the radial direction of the rotary shaft, a thrust bearing that magnetically supports the axial direction of the rotary shaft, and protects the radial bearing and the thrust bearing. In a three-axis control type magnetic bearing device including a protective bearing, the rotary shaft and the protective bearing are formed so as to be in contact with each other, and the rotary shaft and the protective bearing are separated from each other when the rotation of the rotary shaft rises. A magnetic bearing device comprising a control means for controlling to make temporary contact. 2. An inclined surface is formed on at least one of the rotary shaft and the protective bearing at a contact portion between the rotary shaft and the protective bearing so that the rotary shaft and the protective bearing are in contact with each other. The magnetic bearing device according to claim 1, wherein: 3. A rotary shaft, a radial bearing that magnetically supports the radial direction of the rotary shaft, a thrust bearing that magnetically supports the axial direction of the rotary shaft, and protects the radial bearing and the thrust bearing. In a three-axis control type magnetic bearing device including a protective bearing, a rotating shaft whirl-whirling suppressing bearing that suppresses whirling of the rotating shaft is provided, and the rotating shaft whirling occurs when the rotation of the rotating shaft rises. A magnetic bearing device comprising a control means for controlling the suppressing bearing so as to temporarily support the rotating shaft.